Methods to partially reduce a niobium metal oxide and oxygen reduced niobium oxides

ABSTRACT

Methods to at least partially reduce a niobium oxide are described wherein the process includes heat treating the niobium oxide in the presence of a getter material and in an atmosphere which permits the transfer of oxygen atoms from the niobium oxide to the getter material, and for a sufficient time and at a sufficient temperature to form an oxygen reduced niobium oxide. Niobium oxides and/or suboxides are also described as well as capacitors containing anodes made from the niobium oxides and suboxides.

[0001] This application is a divisional application of U.S. patentapplication Ser. No. 09/347,990 filed Jul. 6, 1999, which is acontinuation-in-part of U.S. patent application Ser. No. 09/154,452filed Sep. 16, 1998, and U.S. patent application Ser. No. 60/100,629filed Sep. 16, 1998, which are both incorporated herein in theirentirety by reference.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to niobium and oxides thereof andmore particularly relates to niobium oxides and methods to at leastpartially reduce niobium oxide and further relates to oxygen reducedniobium.

SUMMARY OF THE PRESENT INVENTION

[0003] In accordance with the purposes of the present invention, asembodied and described herein, the present invention relates to a methodto at least partially reduce a niobium oxide which includes the steps ofheat treating the niobium oxide in the presence of a getter material andin an atmosphere which permits the transfer of oxygen atoms from theniobium oxide to the getter material for a sufficient time andtemperature to form an oxygen reduced niobium oxide.

[0004] The present invention also relates to oxygen reduced niobiumoxides which preferably have beneficial properties, especially whenformed into an electrolytic capacitor anode. For instance, a capacitormade from the oxygen reduced niobium oxide of the present invention canhave a capacitance of up to about 200,000 CV/g or more. Further,electrolytic capacitor anodes made from the oxygen reduced niobiumoxides of the present invention can have a low DC leakage. For instance,such a capacitor can have a DC leakage of from about 0.5 nA/CV to about5.0 nA/CV.

[0005] Accordingly, the present invention also relates to methods toincrease capacitance and reduce DC leakage in capacitors made fromniobium oxides, which involves partially reducing a niobium oxide byheat treating the niobium oxide in the presence of a getter material andin an atmosphere which permits the transfer of oxygen atoms from theniobium oxide to the getter material, for a sufficient time andtemperature to form an oxygen reduced niobium oxide, which when formedinto a capacitor anode, has reduced DC leakage and/or increasedcapacitance.

[0006] It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary andexplanatory only and are intended to provide further explanation of thepresent invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIGS. 1-11 are SEMs of various oxygen reduced niobium oxides ofthe present invention at various magnifications.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0008] In an embodiment of the present invention, the present inventionrelates to methods to at least partially reduce a niobium oxide. Ingeneral, the method includes the steps of heat treating a startingniobium oxide in the presence of a getter material in an atmospherewhich permits the transfer of oxygen atoms from the niobium oxide to thegetter material for a sufficient time and at a sufficient temperature toform an oxygen reduced niobium oxide.

[0009] For purposes of the present invention, the niobium oxide can beat least one oxide of niobium metal and/or alloys thereof. A specificexample of a starting niobium oxide is Nb₂O₅.

[0010] The niobium oxide used in the present invention can be in anyshape or size. Preferably, the niobium oxide is in the form of a powderor a plurality of particles. Examples of the type of powder that can beused include, but are not limited to, flaked, angular, nodular, andmixtures or variations thereof. Preferably, the niobium oxide is in theform of a powder which more effectively leads to the oxygen reducedniobium oxide.

[0011] Examples of such preferred niobium oxide powders include thosehaving mesh sizes of from about 60/100 to about 100/325 mesh and fromabout 60/100 to about 200/325 mesh. Another range of size is from −40mesh to about −325 mesh. In other words, the preferred niobium oxidepowders have particle sizes from about 150/250 to about 45/150 microns,and from about 150/250 to about 45/75 microns. Another preferred sizerange is from about 355 microns to about 45 microns.

[0012] The getter material for purposes of the present invention is anymaterial capable of reducing the specific starting niobium oxide to theoxygen reduced niobium oxide. Preferably, the getter material comprisestantalum, niobium, or both. Other examples include, but are not limitedto, magnesium and the like. Any getter material that has a greateraffinity for oxygen than niobium oxide can be used. More preferably, thegetter material is niobium. The niobium getter material for purposes ofthe present invention is any material containing niobium metal which canremove or reduce at least partially the oxygen in the niobium oxide.Thus, the niobium getter material can be an alloy or a materialcontaining mixtures of niobium metal with other ingredients. Preferably,the niobium getter material is predominantly, if not exclusively,niobium metal. The purity of the niobium getter material is notimportant but it is preferred that high purity niobium comprise thegetter material to avoid the introduction of other impurities during theheat treating process. Accordingly, the niobium metal in the niobiumgetter material preferably has a purity of at least about 98% and morepreferably at least about 99%. Oxygen levels in the niobium gettermaterial can be any amount. Preferably, impurities that affect DCleakage, such as iron, nickel, chromium, and carbon, are below about 100ppm. Most preferably, the getter material is a niobium flake metalpreferably having a high capacitance capability, such as greater thanabout 75,000 Cv/g and more preferably about 100,000 Cv/g or higher, suchas about 200,000 Cv/g. The getter material also preferably has a highsurface area, such as a BET of from about 5 to about 30 m²/g and morepreferably from about 20 to about 30 m²/g.

[0013] The getter material can be in any shape or size. For instance,the getter material can be in the form of a tray which contains theniobium oxide to be reduced or can be in a particle or powder size.Preferably, the getter materials are in the form of a powder in order tohave the most efficient surface area for reducing the niobium oxide. Thegetter material, thus, can be flaked, angular, nodular, and mixtures orvariations thereof, e.g., coarse chips, such as 14/40 mesh chips thatcan be easily separated from the powder product by screening.

[0014] Similarly, the getter material can be tantalum and the like andcan have the same preferred parameters and/or properties discussed abovefor the niobium getter material. Other getter materials can be usedalone or in combination with the tantalum or niobium getter materials.Also, other materials can form a part of the getter material.

[0015] Generally, a sufficient amount of getter material is present toat least partially reduce the niobium oxide being heat treated. Further,the amount of the getter material is dependent upon the amount ofreducing desired to the niobium oxide. For instance, if a slightreduction in the niobium oxide is desired, then the getter material willbe present in a stoichemetric amount. Similarly, if the niobium oxide isto be reduced substantially with respect to its oxygen presence, thenthe getter material is present in a 2 to 5 times stoichemetric amount.Generally, the amount of getter material present (e.g., based on thetantalum getter material being 100% tantalum) can be present based onthe following ratio of getter material to the amount of niobium oxidepresent of from about 2 to 1 to about 10 to 1. The getter material ispreferably blended or mixed together with the starting niobium oxide inan atmosphere which permits the transfer of oxygen atoms from theniobium oxide to the getter material (e.g., a hydrogen atmosphere), andpreferably at a temperature of from about 1100° C. to about 1500° C.

[0016] Furthermore, the amount of getter material can also be dependenton the type of niobium oxide being reduced. For instance, when theniobium oxide being reduced is Nb₂O₅, the amount of getter material ispreferably 5 to 1. Also, when starting with Nb₂O₅, a stoichiometricamount of getter material, preferably niobium flake metal, is used toachieve an oxide which preferably is 0.89 parts metal to 1 part oxide.

[0017] The heat treating that the starting niobium oxide is subjected tocan be conducted in any heat treatment device or furnace commonly usedin the heat treatment of metals, such as niobium and tantalum. The heattreatment of the niobium oxide in the presence of the getter material isat a sufficient temperature and for a sufficient time to form an oxygenreduced niobium oxide. The temperature and time of the heat treatmentcan be dependent on a variety of factors such as the amount of reductionof the niobium oxide, the amount of the getter material, and the type ofgetter material as well as the type of starting niobium oxide.Generally, the heat treatment of the niobium oxide will be at atemperature of from less than or about 800° C. to about 1900° C. andmore preferably from about 1000° C. to about 1400° C., and mostpreferably from about 1100° C. to about 1250° C. In more detail, whenthe niobium oxide is a niobium containing oxide, the heat treatmenttemperatures will be from about 1000° C. to about 1300° C., and morepreferably from about 1100° C. to about 1250° C. for a time of fromabout 5 minutes to about 100 minutes, and more preferably from about 30minutes to about 60 minutes. Routine testing in view of the presentapplication will permit one skilled in the art to readily control thetimes and temperatures of the heat treatment in order to obtain theproper or desired reduction of the niobium oxide.

[0018] The heat treatment occurs in an atmosphere which permits thetransfer of oxygen atoms from the niobium oxide to the getter material.The heat treatment preferably occurs in a hydrogen containing atmospherewhich is preferably just hydrogen. Other gases can also be present withthe hydrogen, such as inert gases, so long as the other gases do notreact with the hydrogen. Preferably, the hydrogen atmosphere is presentduring the heat treatment at a pressure of from about 10 Torr to about2000 Torr, and more preferably from about 100 Torr to about 1000 Torr,and most preferably from about 100 Torr to about 930 Torr. Mixtures ofH₂ and an inert gas such as Ar can be used. Also, H₂ in N₂ can be usedto effect control of the N₂ level of the niobium oxide.

[0019] During the heat treatment process, a constant heat treatmenttemperature can be used during the entire heat treating process orvariations in temperature or temperature steps can be used. Forinstance, hydrogen can be initially admitted at 1000° C. followed byincreasing the temperature to 1250° C. for 30 minutes followed byreducing the temperature to 1000° C. and held there until removal of theH₂ gas. After the H₂ or other atmosphere is removed, the furnacetemperature can be dropped. Variations of these steps can be used tosuit any preferences of the industry. The oxygen reduced niobium oxidescan be subsequently reduced in size such as by crushing. The oxygenreduced niobium oxides can be agglomerated and crushed or processed inany other way that valve metals can be processed.

[0020] The oxygen reduced niobium oxides can also contain levels ofnitrogen, e.g., from about 100 ppm to about 30,000 ppm N₂.

[0021] The oxygen reduced niobium oxide is any niobium oxide which has alower oxygen content in the metal oxide compared to the starting niobiumoxide. Typical reduced niobium oxides comprise NbO, NbO_(0.7),NbO_(1.1), NbO₂, and any combination thereof with or without otheroxides present. Generally, the reduced niobium oxide of the presentinvention has an atomic ratio of niobium to oxygen of about 1:less than2.5, and preferably 1:2 and more preferably 1:1.1, 1:1, or 1:0.7. Putanother way, the reduced niobium oxide preferably has the formulaNb_(x)O_(y), wherein Nb is niobium, x is 2 or less, and y is less than2.5x. More preferably x is 1 and y is less than 2, such as 1.1, 1.0,0.7, and the like.

[0022] The starting niobium oxides can be prepared by calcining at 1000°C. until removal of any volatile components. The oxides can be sized byscreening. Preheat treatment of the niobium oxides can be used to createcontrolled porosity in the oxide particles.

[0023] The reduced niobium oxides of the present invention alsopreferably have a microporous surface and preferably have a sponge-likestructure, wherein the primary particles are preferably 1 micron orless. The SEMs further depict the type of preferred reduced niobiumoxide of the present invention. As can be seen in thesemicrophotographs, the reduced niobium oxides of the present inventioncan have high specific surface area, and a porous structure withapproximately 50% porosity. Further, the reduced niobium oxides of thepresent invention can be characterized as having a preferred specificsurface area of from about 0.5 to about 10.0 m²/g, more preferably fromabout 0.5 to 2.0 m²/g, and even more preferably from about 1.0 to about1.5 m²/g. The preferred apparent density of the powder of the niobiumoxides is less than about 2.0 g/cc, more preferably, less than 1.5 g/ccand even more preferably, from about 0.5 to about 1.5 g/cc. Also, thepowder of the niobium oxides can have Scott densities, such as fromabout 5 g/in³ to about 35 g/in³.

[0024] The various oxygen reduced niobium oxides of the presentinvention can be further characterized by the electrical propertiesresulting from the formation of a capacitor anode using the oxygenreduced niobium oxides of the present invention. In general, the oxygenreduced niobium oxides of the present invention can be tested forelectrical properties by pressing powders of the oxygen reduced niobiumoxide into an anode and sintering the pressed powder at appropriatetemperatures and then anodizing the anode to produce an electrolyticcapacitor anode which can then be subsequently tested for electricalproperties.

[0025] Accordingly, another embodiment of the present invention relatesto anodes for capacitors formed from the oxygen reduced niobium oxidesof the present invention. Anodes can be made from the powdered form ofthe reduced oxides in a similar process as used for fabricating metalanodes, i.e., pressing porous pellets with embedded lead wires or otherconnectors followed by optional sintering and anodizing. The leadconnector can be embedded or attached at any time before anodizing.Anodes made from some of the oxygen reduced niobium oxides of thepresent invention can have a capacitance of from about 1,000 CV/g orlower to about 300,000 CV/g or more, and other ranges of capacitance canbe from about 20,000 CV/g to about 300,000 CV/g or from about 62,000CV/g to about 200,000 CV/g and preferably from about 60,000 to 150,000CV/g. In forming the capacitor anodes of the present invention, asintering temperature can be used which will permit the formation of acapacitor anode having the desired properties. The sintering temperaturewill be based on the oxygen reduced niobium oxide used. Preferably, thesintering temperature is from about 1200° C. to about 1750° C. and morepreferably from about 1200° C. to about 1400° C. and most preferablyfrom about 1250° C. to about 1350° C. when the oxygen reduced niobiumoxide is an oxygen reduced niobium oxide.

[0026] The anodes formed from the niobium oxides of the presentinvention are preferably formed at a voltage of about 35 volts andpreferably from about 6 to about 70 volts. When an oxygen reducedniobium oxide is used, preferably, the forming voltages are from about 6to about 50 volts, and more preferably from about 10 to about 40 volts.Other high formation voltages can be used. Anodes of the reduced niobiumoxides can be prepared by fabricating a pellet of Nb₂O₅ with a lead wirefollowed by sintering in H₂ atmosphere or other suitable atmosphere inthe proximity of a getter material just as with powdered oxides. In thisembodiment, the anode article produced can be produced directly, e.g.,forming the oxygen reduced valve metal oxide and an anode at the sametime. Also, the anodes formed from the oxygen reduced niobium oxides ofthe present invention preferably have a DC leakage of less than about5.0 nA/CV. In an embodiment of the present invention, the anodes formedfrom some of the oxygen reduced niobium oxides of the present inventionhave a DC leakage of from about 5.0 nA/CV to about 0.50 nA/CV.

[0027] The present invention also relates to a capacitor in accordancewith the present invention having a niobium oxide film on the surface ofthe capacitor. Preferably, the film is a niobium pentoxide film. Themeans of making metal powder into capacitor anodes is known to thoseskilled in the art and such methods such as those set forth in U.S. Pat.Nos. 4,805,074, 5,412,533, 5,211,741, and 5,245,514, and EuropeanApplication Nos. 0 634 762 A1 and 0 634 761 A1, all of which areincorporated in their entirety herein by reference.

[0028] The capacitors of the present invention can be used in a varietyof end uses such as automotive electronics, cellular phones, computers,such as monitors, mother boards, and the like, consumer electronicsincluding TVs and CRTs, printers/copiers, power supplies, modems,computer notebooks, disc drives, and the like.

[0029] The present invention will be further clarified by the followingexamples, which are intended to be exemplary of the present invention.

Test Methods

[0030] Anode Fabrication:

[0031] size—0.197″ dia

[0032] 3.5 Dp

[0033] powder wt=341 mg

[0034] Anode Sintering:

[0035] 1300 Deg C.* 10′

[0036] 1450 Deg C.* 10′

[0037] 1600 Deg C.* 10′

[0038] 1750 Deg C.* 10′

[0039] 30V Ef Anodization:

[0040] 30V Ef @ 60 Deg C./0.1% H₃PO₄ Electrolyte

[0041] 20 mA/g constant current

[0042] DC Leakage/Capacitance—ESR Testing:

[0043] DC Leakage Testing

[0044] 70% Ef (21 VDC) Test Voltage

[0045] 60 second charge time

[0046] 10% H₃PO₄ @ 21 Deg C.

[0047] Capacitance—DF Testing:

[0048] 18% H₂SO₄ @ 21 Deg C.

[0049] 120 Hz

[0050] 50V Ff Reform Anodization:

[0051] 50V Ef @ 60 Deg C./0.1% H₃PO₄ Electrolyte

[0052] 20 mA/g constant current

[0053] DC Leakage/Capacitance—ESR Testing:

[0054] DC leakage Testing

[0055] 70% Ef (35 VDC) Test Voltage

[0056] 60 second charge time

[0057] 10% H₃PO₄@ 21 Deg C.

[0058] Capacitance—DF Testing:

[0059] 18% H₂SO₄ @ 21 Deg C.

[0060] 120 Hz

[0061] 75V Ef Reform Anodization:

[0062] 75V Ef @ 60 Deg C./0.1% H₃PO₄ Electrolyte

[0063] 20 mA/g constant current

[0064] DC Leakage/Capacitance—ESR Testing:

[0065] DC leakage Testing

[0066] 70% Ef (52.5 VDC) Test Voltage

[0067] 60 second charge time

[0068] 10% H₃PO4 @ 21 Deg C.

[0069] Capacitance—DF Testing:

[0070] 18% H₂SO₄ @ 21 Deg C.

[0071] 120 Hz

[0072] Scott Density, oxygen analysis, phosphorus analysis, and BETanalysis were determined according to the procedures set forth in U.S.Pat. Nos. 5,011,742; 4,960,471; and 4,964,906, all incorporated herebyin their entireties by reference herein.

EXAMPLES Example 1

[0073] +10 mesh Ta hydride chips (99.2 gms) with approximately 50 ppmoxygen were mixed with 22 grams of Nb₂O₅ and placed into Ta trays. Thetrays were placed into a vacuum heat treatment furnace and heated to1000° C. H₂ gas was admitted to the furnace to a pressure of +3 psi. Thetemperature was further ramped to 1240° C. and held for 30 minutes. Thetemperature was lowered to 1050° C. for 6 minutes until all H₂ was sweptfrom the furnace. While still holding 1050° C., the argon gas wasevacuated from the furnace until a pressure of 5×10⁻⁴ torr was achieved.At this point 700 mm of argon was readmitted to the chamber and thefurnace cooled to 60° C.

[0074] The material was passivated with several cyclic exposures toprogressively higher partial pressures of oxygen prior to removal fromthe furnace as follows: The furnace was backfilled with argon to 700 mmfollowed by filling to one atmosphere with air. After 4 minutes thechamber was evacuated to 10⁻² torr. The chamber was then backfilled to600 mm with argon followed by air to one atmosphere and held for 4minutes. The chamber was evacuated to 10⁻² torr. The chamber was thenbackfilled to 400 mm argon followed by air to one atmosphere. After 4minutes the chamber was evacuated to 10⁻² torr. The chamber was thembackfilled to 200 mm argon followed by air to one atmosphere and heldfor 4 minutes. The chamber was evacuated to 10⁻² torr. The chamber wasbackfilled to one atmosphere with air and held for 4 minutes. Thechamber was evacuated to 10⁻² torr. The chamber was backfilled to oneatmosphere with argon and opened to remove the sample. The powderproduct was separated from the tantalum chip getter by screening througha 40 mesh screen. The product was tested with the following results.CV/g of pellets sintered to 1300° C. X 10 minutes and formed to 35 volts= 81,297 nA/CV (DC leakage) = 5.0 Sintered Density of pellets = 2.7 g/ccScott density = 0.9 g/cc Chemical Analysis (ppm) C = 70 H₂ = 56 Ti = 25Fe = 25 Mn = 10 Si = 25 Sn = 5 Ni = 5 Cr = 10 Al = 5 Mo = 25 Mg = 5 Cu =50 B = 2 Pb = 2 all others < limits

Example 2

[0075] Samples 1 through 20 are examples following similar steps asabove with powdered Nb₂O₅ as indicated in the Table. For most of theexamples, mesh sizes of the starting input material are set forth in theTable, for example 60/100, means smaller than 60 mesh, but larger than100 mesh. Similarly, the screen size of some of the Ta getter is givenas 14/40. The getters marked as “Ta hydride chip” are +40 mesh with noupper limit on particle size.

[0076] Sample 18 used Nb as the getter material (commercially availableN200 flaked Nb powder from CPM). The getter material for sample 18 wasfine grained Nb powder which was not separated from the final product.X-ray diffraction showed that some of the getter material remained asNb, but most was converted to NbO_(1.1), and NbO by the process as wasthe starting niobium oxide material Nb₂O₅.

[0077] Sample 15 was a pellet of Nb₂O₅, pressed to near solid density,and reacted with H₂ in close proximity to the Ta getter material. Theprocess converted the solid oxide pellet into a porous slug of NbOsuboxide. This slug was sintered to a sheet of Nb metal to create ananode lead connection and anodized to 35 volts using similar electricalforming procedures as used for the powder slug pellets. This sampledemonstrates the unique ability of this process to make a ready toanodize slug in a single step from Nb₂O₅ starting material.

[0078] The Table shows the high capacitance and low DC leakagecapability of anodes made from the pressed and sintered powders/pelletsof the present invention. Microphotographs (SEMs) of various sampleswere taken. These photographs show the porous structure of the reducedoxygen niobium oxide of the present invention. In particular, FIG. 1 isa photograph of the outer surface of a pellet taken at 5,000× (sample15). FIG. 2 is a photograph of the pellet interior of the same pellettaken at 5,000×. FIGS. 3 and 4 are photographs of the outer surface ofthe same pellet at 1,000×. FIG. 5 is a photograph of sample 11 at 2,000×and FIGS. 6 and 7 are photographs taken of sample 4 at 5,000×. FIG. 8 isa photograph taken of sample 3 at 2,000× and FIG. 9 is a photograph ofsample 6 at 2,000×. Finally, FIG. 10 is a photograph of sample 6, takenat 3,000× and FIG. 11 is a photograph of sample 9 taken at 2,000×. TABLEXRD* XRD* XRD* XRD* Sam- Temp Time Hydrogen Major Major Minor Minor1300X35v 1300X35v ple Input Material Gms Input Getter Gms (° C.) (min)Pressure 1** 2** 1*** 2*** CV/g na/CV 1 −40 mesh 20(est) Ta hydridechips 40 (est) 1240 30 3 psi 81297 5 calcined Nb₂O₅ 2 60/100 Nb₂O₅ 23.4Ta hydride chips 65.4 1250 30 3 psi NbO_(1.1) NbO TaO 115379 1.28 360/100 Nb₂O₃ 23.4 Ta hydride chips 65.4 1250 30 3 psi NbO_(1.1) NbO TaO121293 2.19 4 100/325 Nb₂O₅ 32.3 Ta hydride chips 92.8 1250 30 3 psi113067 1.02 5 100/325 Nb₂O₅ 32.3 Ta hydride chips 92.8 1250 30 3 psi145589 1.42 6 60/100 Nb₂O₅ 26.124 Ta hydride chips 72.349 1250 90 3 psi17793 12.86 7 60/100 Nb₂O₅ 26.124 Ta hydride chips 72.349 1250 90 3 psi41525 5.63 8 200/325 Nb₂O₅ 29.496 Ta hydride chips 83.415 1250 90 3 psi17790 16.77 9 60/100 Nb₂O₅ 20.888 Ta hydride chips 60.767 1200 90 3 psiNbO_(1.1) NbO Ta₂O₃ 63257 5.17 10 60/100 Nb₂O₅ 20.888 Ta hydride chips60.767 1200 90 3 psi NbO_(1.1) NbO Ta₂O₃ 69881 5.5 11 200/325 Nb₂O₅23.936 Ta hydride chips 69.266 1200 90 3 psi NbO_(1.1) NbO Ta₂O₅ 617166.65 12 200/325 Nb₂O₅ 23.936 Ta hydride chips 69.266 1200 90 3 psiNbO_(1.1) NbO Ta₂O₃ 68245 6.84 13 200/325 Nb₂O₅ 15.5 14/40 Ta hydride41.56 1250 30 3 psi NbO_(0.7) NbO TaO NbO₂ 76294 4.03 14 200/325 Nb₂O₅10.25 14/40 Ta hydride 68.96 1250 30 3 psi NbO_(0.7) NbO TaO NbO₂ 2928121.03 15 Nb₂O₅ pellets 3.49 14/40 Ta hydride 25.7 1250 30 3 psi 708400.97 16 200/325 Nb₂O₅ 13.2 14/40 Ta hydride 85.7 1200 30 3 psi NbO₂NbO_(0.7) TaO NbO 5520 34.33 17 200/325 Nb₂O₅ 14.94 14/40 Ta hydride41.37 1200 30 3 psi 6719 38.44 18 200/325 Nb₂O₅ 11.92 N200 Nb powder21.07 1200 30 3 psi Nb NbO_(1.1) NbO 25716 4.71 19 200/325 Nb₂O₅ 1014/40 Ta hydride 69 1250 30 100 Torr 108478 1.95 20 200/325 Nb₂O₅ 1614/40 Ta hydride 41 1250 30 100 Torr 106046 1.66

[0079] Other embodiments of the present invention will be apparent tothose skilled in the art from consideration of the specification andpractice of the invention disclosed herein. It is intended that thespecification and examples be considered as exemplary only, with a truescope and spirit of the invention being indicated by the followingclaims.

What is claimed is:
 1. A method to at least partially reduce a niobiumoxide comprising heat treating the niobium oxide in the presence of aniobium flaked getter material and in an atmosphere which permits thetransfer of oxygen atoms from the niobium oxide to the niobium flakedgetter material, for a sufficient time and temperature to form an oxygenreduced niobium oxide.
 2. The method of claim 1, wherein the niobiumoxide is a niobium pentoxide.
 3. The method of claim 1, wherein theoxygen reduced niobium oxide is a niobium suboxide.
 4. The method ofclaim 1, wherein the oxygen reduced niobium oxide has a niobium tooxygen atomic ratio of 1:less than 2.5.
 5. The method of claim 1,wherein the oxygen reduced niobium oxide has oxygen levels that are lessthan stoichemetric for a fully oxidized niobium.
 6. The method of claim1, wherein the oxygen reduced niobium oxide has a micro-porousstructure.
 7. The method of claim 1, wherein the oxygen reduced niobiumoxide has a pore volume of about 50%.
 8. The method of claim 1, whereinthe hydrogen atmosphere is present in an amount of about 10 Torr toabout 2000 Torr.
 9. The method of claim 1, wherein the niobium flakedgetter material is capable of a capacitance of at least 75,000 Cv/g whenformed into an anode.
 10. The method of claim 1, wherein the atmosphereis a hydrogen atmosphere.
 11. The method of claim 1, wherein the niobiumflaked getter material is capable of a capacitance of at least about100,000 Cv/g when formed into an anode.
 12. The method of claim 1,wherein the niobium flaked getter material is capable fo a capacitanceof from about 120,000 Cv/g to about 200,000 Cv/g when formed into ananode.
 13. The method of claim 1, wherein said heat treating is at atemperature of from about 1100° C. to about 1500° C. and for about 10 toabout 90 minutes.
 14. The method of claim 1, wherein said niobium flakedmaterial is homogenized with the niobium oxide prior to or during theheat treating step.
 15. A method to at least partially reduce a niobiumoxide comprising heat treating the niobium oxide in the presence of amagnesium containing getter material and in an atmosphere which permitsthe transfer of oxygen atoms from the niobium oxide to the magnesiumcontaining getter material, for a sufficient time and temperature toform an oxygen reduced niobium oxide.
 16. The method of claim 15,wherein said magnesium containing getter material is homogenized withthe niobium oxide prior to or during the heat treating step.
 17. Amethod of making a capacitor anode comprising a) fabricating a pellet ofniobium oxide and heat treating the pellet in the presence of a niobiumflaked getter material or magnesium containing getter material, and inan atmosphere which permits the transfer of oxygen atoms from theniobium oxide to the niobium flaked getter material or magnesiumcontaining getter material, and for a sufficient time and temperature toform an electrode body comprising the pellet, wherein the pelletcomprises an oxygen reduced niobium oxide, and b) anodizing saidelectrode body to form said capacitor anode.
 18. The method of claim 17,wherein the atmosphere is a hydrogen atmosphere.
 19. The method of claim17, wherein the getter material is flaked niobium.
 20. The method ofclaim 17, wherein the oxygen reduced niobium oxide has an atomic ratioof niobium to oxygen of 1:less than 2.5.